The present disclosure relates to apparatus for coupling trailers, and more particularly, but not by way of limitation, to a retractable, combination support member and jack for trailer tongues. The present invention is an improved means for stable support of a trailer independently detached from a towing vehicle, and an improved means for retraction of the support means when the trailer is coupled for travel mode.
For safety and operational reasons, the main axle on a conventional trailer is located behind the trailer's center of gravity. This common design causes the weight of the trailer to bear primarily on the tongue of the trailer's coupling. Therefore, with most conventional trailers, a jack is necessary to raise the tongue when coupling with a towing vehicle. This makes a jack mounted onto the tongue highly desirable. It is also desirable for trailer frames to remain horizontal when detached from towing vehicles. Consequently, most jacks on trailer tongues are designed to function as both a jack and a support member. For further convenience, the combined jacking and supporting apparatus is retractable when the trailer is towed by a powered vehicle.
In the past, several attempts were made to incorporate all of the above desired features. U.S. Pat. Nos. 3,863,894, 2,784,985, and 2,153,722 all disclose mounted jacks which can serve as supporting means when the trailer is uncoupled and capable of retraction when the trailer is being towed. All three references disclose devices which have a single, vertically oriented supporting member. This single support member is vulnerable to various design stresses. Such stresses include extraneous vibrations over the surface supporting the trailer such as from movement by passing vehicles, and lateral forces acting on the trailer frame such as those created when heavy objects are loaded into a freight trailer or from movement within a recreational trailer. If such stress is of sufficient magnitude or is cumulatively exerted over time, the connection between the supporting member and the tongue will undergo structural failure.
Some prior art recognize the structural instability of single support members. For example, U.S. Pat. No. 2,672,318 discloses a single support member pivotally connected at one end to a trailer tongue and pivotally connected at the opposite end to a jack. This design provides some stability for forward and backward "rocking" stresses because the supporting member exerts a torque at its point of attachment to the trailer tongue. However, the design is still vulnerable to lateral stresses.
Another design consideration inadequately addressed by prior art is the weight-to-strength ratio of support members in relation to retractability. For increased stability, support members have to have more structural components, which logically increases weight. Additionally, heavier structural materials can be substituted for existing components of support means to provide greater stability. However, enhancing stability increases the overall weight of the support means, which compromises the ease of retractability. There is a need, therefore, for supplemental mechanical means to assist in the retraction of heavy support members to decrease the amount of lifting force required.
The problems abundant in the prior art are overcome with the present invention. The following specification discloses a retractable, combination jack and support apparatus comprising a jack both pivotally connected to a support frame and pivotally connected to a trailer tongue. The support frame is designed to withstand lateral, forward and backward stresses, and is of a heavy, sturdy construction. The jack with its two pivotal connections combined with a counterbalance form a pivot arm and an integral counterweight which creates a mechanical and physical advantage to the retraction and lowering of the support frame.